Electrostatic chuck device

ABSTRACT

An electrostatic chuck device provided with a dielectric plate with a surface embossed to give it a plurality of projections, an electrode, and an external power source, wherein substrate supporting surfaces of the plurality of projections are covered by conductor wiring and the conductor wiring electrically connects the substrate supporting surfaces of the plurality of projections. At the time of substrate processing, when the embossed projections contact the back of the substrate, the back of the substrate and the conductor wiring is made the same in potential due to the migration of the charges, the generation of force between the back of the substrate and the conductor wiring being in contact with the same is prevented, and a rubbing state between the two is prevented. Due to this, the electrostatic chuck device reduces the generation of particles, easily and stably removes and conveys substrates, and realizes a high yield and system operating rate.

This is a Continuation of application Ser. No. 12/289,207, filed Oct.22, 2008, pending, which in turn is a Continuation of application Ser.No. 10/462,765 filed Jun. 17, 2003. The disclosure of the priorapplications is hereby incorporated by reference herein in theirentirety.

BACKGROUND

1. Field of the Invention

The present invention relates to an electrostatic chuck device, moreparticularly to an electrostatic chuck device for chucking and fixing asubstrate in a substrate processing chamber in a semiconductorproduction process.

2. Description of the Related Art

In recent years, in processing substrates or wafers such as theformation or deposition of a thin film on a substrate (sputtering,chemical vapor deposition (CVD), etc.) or dry etching in a semiconductorproduction process, electrostatic chuck devices are frequently used forfixing the substrates or wafers onto a wafer holder. In comparison withthe conventional mechanical clamping units, when fixing a substrate, anelectrostatic chuck mechanism does not have any parts for touching andholding the upper surface of the substrate. Accordingly, a percentage ofdevices obtained from one substrate becomes high and a yield rate of thedevices can be raised. Further, precise control of the temperaturethrough a combination with a temperature regulator becomes possible.

Electrostatic chuck (ESC) devices are divided into two types. One is aunipolar type and another is a bipolar type. Operation of a unipolardevice requires plasma over the entire surface of the substrate. Thisplasma creates the electrical connection required for generating anelectrostatic force. A bipolar device, however, operates even withoutplasma. Therefore, generally, the electrostatic chuck devices can beused for both plasma process and non-plasma process.

An example of a conventional electrostatic chuck device will beexplained with reference to FIG. 23. This electrostatic chuck device isapplied to a sputtering system, for example. In this sputtering system,the pressure inside of a metal vessel 11 is reduced in pressure by anevacuation mechanism (not shown). A disk-shaped target 13 supported by aring-shaped insulating member 12 is attached to the ceiling part of thevessel 11. In the outside of the vessel 11, magnets 15 fixed to a yoke14 are placed at the back of the target 13. At the lower section of theinside of the vessel 11, a substrate support 16 is provided. A substrate17 is loaded on the top surface of the substrate support 16. Thesubstrate 17 is arranged to face the target 13 in parallel to it. Thesubstrate support 16 is fixed to the bottom of the vessel 11. Thesubstrate support 16 is provided with an electrostatic chuck device 18and a substrate temperature regulator 19. A cylindrical shield 20 isprovided near the inside surface of the surrounding walls of the vessel11.

The electrostatic chuck device 18 is comprised of a dielectric plate 22on the surface of which an embossed part 21 is formed by an embossingprocess, and a metal electrode 23 arranged at the inside of thedielectric plate 22. The height of the embossed part is 5 to 25 μm. Themetal electrode 23 has, for example, a bipolar electrode structurecomprised of an inside electrode 23 a and outside electrode 23 b. Themetal electrode 23 is connected to an external DC power circuit 24 andsupplied with a certain voltage. The external DC power circuit 24includes a battery 24 a for supplying a plus voltage, a battery 24 b forsupplying a minus voltage, a ground terminal 24 c, and switches 24 d and24 e. The inside electrode 23 a is supplied with a plus voltage by thebattery 24 a, while the outside battery 23 b is supplied with a minusvoltage by the battery 23 b, for example. The substrate (siliconsubstrate) 17 is fixed on the substrate support 16 by the coulomb force(electrostatic force) acting between the metal electrode 23 and thesubstrate 17 when it is placed on the dielectric plate 22 and apredetermined voltage is supplied to the metal electrode 23. The coulombforce is generated by the charges induced at the surface of thedielectric plate 22. The substrate 17 is clamped on the surface of thedielectric plate 22 by the coulomb force.

The substrate temperature regulator 19 is provided below theelectrostatic chuck device 18. The substrate temperature regulator 19 iscomprised of a thermocouple 25, a power source/control mechanism 26, anda heating/cooling unit 27. The cooling/heating unit 27 is controlled toa required predetermined temperature by the thermocouple 25 and powersource/control mechanism 26 and holds the dielectric plate 22 providedon it at a predetermined temperature. The temperature of the substrate17 on the embossed part 21 of the dielectric plate 22 is held at apredetermined temperature by heat conduction of a gas introduced intothe clearances 21 a formed by the embossed part 21 by a gas supplysource 28 and gas introduction path 29, and the clearances 21 a are heldat a predetermined pressure.

When the substrate 17 is clamped by the electrostatic chuck device 18,the clamping force has to be sufficiently larger than the force due tothe differential pressure between the pressure in the clearances 21 aand the internal pressure of the vessel 11. The normal sputteringpressure is several milli-torrs (mTorr). Therefore, the value of thedifferential pressure is substantially equal to the pressure of theclearances 21 a. In this case, the value of the differential pressure isabout 10 Torr.

The force clamping the substrate 17 is the coulomb force acting betweenthe surface of the dielectric plate 22 and the substrate 17. The coulombforce will be explained with reference to FIG. 24 and FIG. 25.

The substrate 17 is placed on the embossed part 21 of the dielectricplate 22. As shown in FIG. 24, when a plus voltage is supplied to themetal electrode 23 (inside electrode 23 a) from the battery 24, pluscharges are induced on the surface of the dielectric plate 22, andsimultaneously minus charges are induced on the back of the substrate17.

When the unipolar electrode is used as the metal electrode, thesubstrate 17 is electrically connected to the ground for the powersource through the plasma and a closed circuit is formed. When thebipolar electrode is used as the metal electrode, charges appear at theback of the dielectric plate 22 corresponding to each of plus and minusvoltages of the internal and external electrodes. A closed circuit isformed through the back surface of the substrate 17, and the charges areinduced on the back surface of the substrate 17. Due to the formation ofthe closed-circuit for a DC current via the back surface of thesubstrate, the substrate gets electrostatically chucked without aplasma.

The force (F) acting between the surface of the dielectric plate 22 andthe substrate 17 satisfies F=∈(V²/L²)A/2 in the case of the unipolarelectrode, while it satisfies F=∈(V²/L²)A/8 in the case of the bipolarelectrode with the same plus and minus electrode areas. Here, ∈ is thedielectric constant of the clearances 21 a, V is the voltage, L is thedistance between the dielectric plate and the back of the substrate(back of silicon substrate), and A is the electrode area. The clampingforce is proportional to the supplied voltage and electrode area and isinversely proportional to the distance between the substrate and thedielectric plate. In sputtering, it is necessary to heat the substratebefore film formation and to hold it at a predetermined temperature, sousually the bipolar electrode is used.

On the other hand, at projections 21 b of the embossed part 21 where thesubstrate 17 and the dielectric plate 22 come into direct contact, asshown in FIG. 25, fine clearances 30 (distance δ of clearances) aregenerated due to the fine projections and recesses on the surface of thesubstrate 17 or dielectric plate 22. The distance δ of the clearances 30is extremely small or about 0.1 μm, so the force generated across theclearances 30 becomes extremely large. This is called the“Johnsen-Rahbek effect” (“JR effect”).

The clamping force will be calculated for the case of the bipolarelectrode. When processing a substrate whose diameter is 300 mm, it isassumed that the diameter of the dielectric plate 22 is 300 mm, and theouter periphery with 1 mm of the dielectric plate 22 and the embossedprojections contact the substrate and support it. The surface area ofthe contact sections becomes 1% of the horizontal area of the entiredielectric plate. As the metal electrode 23, a bipolar electrode splitinto two to form an inside circle and an outside ring is used. The metalelectrode 23, for calculation purposes, is assumed to be a disk with adiameter of 298 mm. The voltage supplied to the metal electrode is made+200 V for the plus electrode and −200 V for the minus electrode. Theemboss gap (difference in height between the projections and recesses)corresponding to the distance L between the substrate 17 and thedielectric plate 22 is 7 μm, while the fine clearance 6 of the contactparts between the embossed projections 21 b and the substrate is 0.1 μm,for example. Further, the clamping force is assumed to act on thesurface of the dielectric plate in only the vertical direction.

The force acting on the depressions of the embossed part 21 becomes 500N to 600 N and the force acting on the projections 21 b becomes 5000 Nto 10000 N. Therefore, the whole force on the embossed part 21 becomes5500 N to 10600 N. The force acting on the projections 21 b is extremelylarge and important in control. The total of these forces acts on thesubstrate as a whole, but the force per unit area, or the pressure,becomes 500 Torr to 1000 Torr. This pressure is sufficiently larger thanthe force due to the differential pressure between the pressure of theclearances between the substrate 17 and the dielectric plate 22 and theinternal pressure of the vessel 11, so the substrate 17 is stablyclamped and fixed on the dielectric plate 22.

Next, the sputtering process for the substrate 17 in the vessel 11 ofthe sputtering system will be explained.

The substrate 17 is carried into the vessel 11 and placed on thedielectric plate 22 of the substrate support 16. The substrate 17 isconveyed by a not shown conveyance robot and lift pins. Next, theexternal DC power circuit 24 is operated and predetermined voltages aresupplied to the electrode 23. In this example, +200 V is supplied to theinternal electrode 23 a, while −200 V is supplied to the externalelectrode 23 b. The internal electrode 23 a and the external electrode23 b are supplied with the same voltages in absolute value. When theelectrode 23 is supplied with voltages, as explained above, theelectrostatic force clamps and fixes the substrate 17 to the dielectricplate 22. When the substrate 17 is fixed, a gas is introduced to theclearances 21 a formed between the substrate 17 and the dielectric plate22 from a gas supply source 28 through a gas introduction path 29. Thepressure within the clearances 21 a is controlled to a certainpredetermined pressure in the range of 1 Torr to 10 Torr. Due to thisgas, heat is conducted from the dielectric plate 22 held at apredetermined temperature by the substrate temperature regulator 19 tothe substrate 17. As a result, the substrate 17 also rises intemperature and is held at a predetermined temperature. When thesubstrate temperature reaches a certain level, Ar gas is introduced intothe vessel 11 and the pressure within the vessel 11 is held at apredetermined pressure. Next, the target 13 facing the substrate 17 issupplied with a high voltage from a sputter power source 31, electricdischarge occurs within the vessel 11, and a desired thin film is formedon the substrate 17 by the sputtering action on the target 13. After theformation of the film ends, the introduction of gas into the inside ofthe vessel and the supply of gas into the clearances 21 a are stopped.After the pressure sufficiently falls, the supply of voltage to theelectrode 23 is stopped. Next, not shown lift pins are used to separatethe substrate 17 from the embossed part 21 of the dielectric plate 22and a conveyance robot which is similarly not shown is used to conveythe substrate 17 out of the vessel 11.

According to the above configuration of the conventional electrostaticchuck device, two important problems of the generation of particles anddeclamping of the substrate explained below arise.

Problem of generation of particles: The conventional electrostatic chuckdevice is set so that the clamping force between the substrate 17 andthe embossed part 21 of the dielectric plate 22 becomes strong.Therefore, as problems, it has arisen that at the time of start ofclamping, the back of the substrate 17 rubs against the dielectric plate22 and the substrate 17 is abraded, and accordingly large amounts ofparticles are generated and become sources of dust causing a drop inyield.

As shown in FIG. 25, the substrate 17 and the top surfaces of theprojections 21 b of the embossed part 21 at the dielectric plate 22 comeinto contact at several points. These contact points form clearances 30between the substrate 17 and the projections 21 b. The clearance 30 isin a vacuum state or filled with an inert gas. Therefore, in calculatingthe electrostatic force, a large clamping force is generated by thedistance of “δ” shown in FIG. 25. This means that the substrate isbasically fixed on the electrostatic chuck device 18 by the forcegenerated on the embossed part. That is, at the back of the substrate17, an extremely large pressure is present on a smaller surface area. Asa result, the substrate 17 and the dielectric plate 22 are abraded byfriction and fine particles are generated. Part of these particlesdirectly sticks on the back of the substrate, while the remainder fallsinto the depressions (or clearances 21 a) of the embossed part 21 and isdeposited there. With repeated processing of a substrate 17, the numberof particles deposited in the depressions increases and the particlesstart to stick on the back of the substrate. The particles stick on theback of the substrate for two reasons. The first reason is theelectrostatic force generated between the substrate and the particles.The second reason is that the particles start floating freely due to therapid flow of the inert gas through the clearances 21 a between thesubstrate and the dielectric plate. These free-floating particles canstick on the back of the substrate.

To solve the problem of the generation of particles, it is sufficient toreduce the area of the parts of the projections 21 b contacting thesubstrate. Since these parts have the function of supporting the flexingsubstrate, however, there are limits to the reduction of the area.

Problem of declamping of substrate: The charge given at the surface ofthe dielectric plate 22 remains even after stopping the supply ofvoltage to the metal electrode 23 after processing the substrate 17, sothe clamping force does not immediately dissipate.

The problem of declamping will be explained considering theabove-mentioned hardware configuration and formula for obtaining theelectrostatic force. To declamp the substrate, the electrodes 23 a and23 b of the metal electrode 23 are disconnected from the batteries 24 aand 24 b and connected to the ground by operating the switches 24 d and24 e.

When a DC voltage is given to the electrodes 23 a and 23 b, firstcharges build up on the electrodes 23 a and 23 b. These charges migrateslowly toward the dielectric plate 22, that is, the top surface of theembossed part 21, due to the presence of the strong electric field (E₁:shown in FIG. 24) generated between the substrate 17 and the electrodes23 a and 23 b. The migration of the charges to the top surface of theembossed part 21 is due to the fact that the dielectric plate 22normally is not a perfect insulator. Further, the dielectric plate 22 isdeliberately doped with an impurity to reduce the electrical resistance.Finally, the charges accumulated on the top surface of the dielectricplate 22 or the top surface of the embossed part 21.

On the microscopic scale, the lower surface of the substrate 17 and thetop surfaces of the projections 21 b of the embossed part 21 are rough.Actual contact between the substrate and the dielectric plate 22 occursonly at a few locations as shown by FIG. 25. Due to the accumulation ofcharges on the top surface of the dielectric plate 22 (the top surfaceof the embossed part 21), the above electrical field (E₁) is reduced.Instead, the electrical field between the top surfaces of theprojections 21 b of the embossed part 21 and the substrate 17 becomesstronger. The charges generated on the top surface of the dielectricplate 22 fall along with the elapse of time. Therefore, even if noproblem arises with respect to fixing the substrate by the electrostaticforce, a problem arises in the operation to release the substrate whichhas been clamped. The reason is that when the electrodes 23 a and 23 bare connected to the ground to release the substrate, the charges on thetop surface of the dielectric plate 22 will not immediately flow back tothe electrodes 23 a and 23 b. Re-flow of the charges of the electrodes23 a and 23 b depends on the electrical resistance of the dielectricplate 22. To facilitate the re-flow of the charges to the metalelectrodes 23 a and 23 b, the dielectric plate 22 is doped with animpurity so as to reduce its electrical resistance. However, due to there-flow of charges to the metal electrode, the electrical field in thedielectric plate 22 is weakened and therefore the re-flow of the chargesgradually slows along with the elapse of time. In this way, the completeneutralization of the dielectric plate 22 by the charge re-flow processrequires considerable time. Accordingly, swift release of the substratecannot be readily achieved.

Therefore, if trying to separate the substrate 17 from the dielectricplate 22 by lift pins for the purpose of conveying the substrate 17outside of the vessel 11, the substrate will generate a vibration and adeviation in position. As a result, the problems of deterioration ofdistribution of the charges and inability of conveyance etc. will occurin the later substrate processing, and further the problems of a drop inyield or a drop in system operating rate will be caused.

As a prior art related to the above problems, the electrostatic chuckdevice disclosed in Japanese Unexamined Patent Publication (Kokai) No.11-251416 may be further mentioned. With this electrostatic chuckdevice, a good releasability of the clamped object is realized.

As further related art, U.S. Pat. No. 5,530,616 and J. Daviet, L.Peccoud, J. Electrochem. Soc., Electrochemical Association, November,1993, vol. 140, No. 11, pp. 3251-3256 may be mentioned.

SUMMARY

An object of the present invention is to provide an electrostatic chuckdevice reducing the generation of particles, easily and stably removingand conveying substrates, and realizing a high yield and systemoperating rate.

The electrostatic chuck device according to the present invention isconfigured as follows to achieve the above object.

According to a first aspect of the present invention, there is providedan electrostatic chuck device provided with a dielectric plate having asurface embossed to be provided with a plurality of projections, anelectrode, and an external power source, wherein substrate supportingsurfaces of the plurality of projections are covered by conductor wiringand the conductor wiring electrically connect the substrate supportingsurfaces of the plurality of projections.

The above electrostatic chuck device is configured to clamp a substrateby the coulomb force acting between the surface of the dielectric plateand the back of the substrate. In this configuration, all of the topsurfaces of the plurality of embossed projections contacting the back ofthe substrate to support the substrate are covered by the conductorwiring, and the conductor wiring electrically connects the plurality ofembossed projections. Therefore, when the embossed projections contactwith the back of the substrate in substrate processes, the back of thesubstrate and the conductor wiring come to be same potential due to themigration of the charges, the generation of force between the back ofthe substrate and the conductor wiring is prevented, and a rubbing statebetween the two is prevented.

Preferably, the electrostatic chuck device is further provided with aswitch for switching the conductor wiring to be in a grounded state orin a floating state. When processing a substrate, the conductor wiringis held in the floating state by the switch to cause the above-mentionedaction. when the processes of treating the substrate are completed, theswitch is used to place the conductor wiring in the grounded state,whereby the charges generated at the embossed projections, the back ofthe substrate, and the surface of the dielectric plate are released andthe clamping force is made to quickly dissipate.

Alternatively, the electrostatic chuck device is further provided with aconductor shaft at the center of the dielectric plate, through which theconductor wiring is connect to the switch.

More preferably, the material of the conductor wiring is an abrasionresistant metal or its alloy. It is possible to suppress the generationof particles by using the abrasion resistant metal for the conductorwiring.

Alternatively, more preferably, parts of the electrode, which arecorresponding to the plurality of projections and near them, areremoved. By removing these parts of the electrode, the amounts ofcharges at the top surfaces of the projections can be reduced and thecoulomb force between the embossed projections and the substrate can bereduced.

According to a second aspect of the present invention, an electrostaticchuck device is provided with a dielectric plate with an embossedsurface, an electrode layer formed in the embossed depressions, anexternal power source for placing the electrode layer in one of a statesupplied with voltage and a grounded state, and conductor layers formedon substrate supporting surfaces of the embossed projections.

The above electrostatic chuck device may be used for substrateprocessing systems such as a sputtering system. The substrate fixed bythe electrostatic chuck device is a silicon substrate etc. The surfaceof the dielectric plate is formed with embossed part by embossmentprocessing. The embossed part is formed to have projections,depressions, and an outer peripheral projection. When the electrodelayer formed at the embossed depressions is supplied with voltage, acharge is induced at the back of the substrate. The sections being incontact with the substrate are the conductor layers formed on thesurfaces of the embossed projections, so the contact parts become thesame potential as the substrate and no electrostatic force is generated.Therefore, it becomes possible to suppress the generation of particlesdue to rubbing. Note that the conductor layer is similarly formed at thesurface of the outer peripheral projection as well. The embossedprojections are defined as including the outer peripheral projection inconcept. Further, if the electrode layer is grounded after theprocessing of the substrate, the induced charges can be rapidlyreleased.

Preferably, a step difference formed between the electrode layer and theconductor layers is in a range of several μm to several tens of μm,particularly preferably a range of 5 μm to 30 μm.

Alternatively, the electrode layer is divided in the same plane and theresultant plurality of electrode layer sections are insulated from eachother. With this configuration, a bipolar electrode layer comprised ofan inside electrode layer and an outside electrode layer is formed.

Alternatively, the range where the conductor layers are formed is insidefrom the range of the surfaces of the embossed projections. With thisconfiguration, the edges of the conductor layer and the edges of theelectrode layer are prevented from being arranged linearly in the heightdirection.

Alternatively, the range where the conductor layers are formed is insidefrom the range of the surfaces of the embossed projections and theelectrode layer is not formed around the embossed projections. With thisconfiguration as well, the edges of the conductor layers and the edgesof the electrode layer are prevented from being arranged linearly in theheight direction.

More preferably, the materials of the electrode layer and the conductorlayers are tungsten, molybdenum, tantalum, or a carbon-based conductor.

According to a third aspect of the present invention, a unipolar typeelectrostatic chuck device used for fixing a substrate, is comprised ofa metal electrode having a plurality of embossed projections on its topsurface, dielectric layers formed on the surfaces of the plurality ofembossed projections, an insulator covering the metal electrode exceptfor the top surface of the metal electrode, and a DC power sourceconnected to the metal electrode.

According to a fourth aspect of the present invention, a bipolar typeelectrostatic chuck device used for fixing a substrate, is comprised oftwo metal electrodes having pluralities of embossed projections on theirtop surfaces and electrically insulated from each other, dielectriclayers formed on the surfaces of the pluralities of embossedprojections, an insulator covering the metal electrodes except for thetop surfaces of the metal electrodes, and two DC power sources connectedto the two metal electrodes in a separated state.

The electrostatic chuck devices of the third aspect and fourth aspect ofthe present invention may be further configured as follows. Thedielectric layers may be made to cover the entire top surface orsurfaces of the metal electrode or electrodes provided with the embossedprojections. The height of the embossed projections may be made largerthan 10 μm and the thickness of the dielectric layers smaller than 1 μm.The metal electrode or electrodes may have a mechanism for cooling orheating for maintaining desired temperatures on the metal electrode orelectrodes. Further, in the present invention, the metal electrode orthe two metal electrodes may be supplied with an rf current of afrequency in a range of 100 kHz to 100 MHz. The two metal electrodes maybe connected to a single rf power source operating at a frequency in arange of 100 kHz to 100 MHz.

As explained above, the electrostatic chuck device for fixing thesubstrate on the electrode is characterized by providing embossedprojections on a metal electrode considerably taller than theconventional device and by forming dielectric thin films much thinnerthan the conventional device on the top surfaces of the embossedprojections. This configuration reduces the occurrence of particles,reduces the sticking of particles on the back of the substrate, andfacilitates the process of releasing the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clearer from the following description of the preferredembodiments given with reference to the attached drawings, wherein:

FIG. 1 is a longitudinal sectional view of a sputtering system to whichan electrostatic chuck device according to a first embodiment of thepresent invention is applied;

FIG. 2 is a plan view of a pattern of arrangement of an embossed part ofa dielectric plate and a metal electrode;

FIG. 3 is a plan view of the pattern of conductor wiring formed on thesurface of the dielectric plate;

FIG. 4 is a sectional view along the line A-A in FIG. 2;

FIG. 5 is an enlarged plan view of main parts for explaining therelationship among the embossed projections, the conductor wiring, andthe metal electrode;

FIG. 6 is a sectional view along the line B-B in FIG. 5;

FIG. 7 is a longitudinal sectional view of a sputtering system to whichan electrostatic chuck device according to a second embodiment of thepresent invention is applied;

FIG. 8 is an enlarged longitudinal sectional view of the state ofcontact between the embossed part of the dielectric plate and asubstrate;

FIG. 9 is a plan view of the pattern of arrangement of the embossed partof the dielectric plate and an electrode layer;

FIG. 10 is an enlarged longitudinal sectional view of another example ofthe state of contact between the embossed part of the dielectric plateand the substrate;

FIG. 11 is an enlarged longitudinal sectional view of the state wherethe substrate is separated in another example of the state of contactbetween the embossed part of the dielectric plate and the substrate;

FIG. 12 is an enlarged longitudinal sectional view of the supply ofvoltage and the induced charges in the state of contact between theembossed surface of the dielectric plate and the substrate;

FIG. 13 is a longitudinal sectional view of key parts of anelectrostatic chuck device according to a third embodiment of thepresent invention;

FIG. 14 is an enlarged sectional view of a circle section A shown byFIG. 13;

FIG. 15 is an enlarged sectional view of the configuration of embossedprojections and the distribution of charges at the metal electrode andsubstrate in a third embodiment;

FIG. 16 is an enlarged sectional view of the distribution of charges atthe top parts of the embossed projections;

FIG. 17 is an enlarged sectional view of the state of distribution ofcharges between two embossed projections where particles haveaccumulated;

FIG. 18 is a longitudinal sectional view of main parts of anelectrostatic chuck device according to a fourth embodiment of thepresent invention;

FIG. 19 is an enlarged sectional view of a circle section B shown inFIG. 18;

FIG. 20 is a sectional view of main parts of an electrostatic chuckdevice according to a fifth embodiment of the present invention;

FIG. 21 is a sectional view of main parts of an electrostatic chuckdevice according to a sixth embodiment of the present invention;

FIG. 22 is an enlarged sectional view of the top surface of a metalelectrode used in a seventh embodiment of the present invention;

FIG. 23 is a longitudinal sectional view of a sputtering system providedwith a conventional electrostatic chuck device;

FIG. 24 is a partial enlarged longitudinal sectional view for explainingthe contact relationship between an embossed part of a dielectric plateand a substrate in the conventional electrostatic chuck device; and

FIG. 25 is a partial enlarged longitudinal sectional view for explainingthe contact relationship between the embossed projections and thesubstrate in the conventional electrostatic chuck device.

DETAILED DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention will be described indetail below in referring to the attached figures. The configurations,shapes, sizes, and relative arrangements explained in the followingembodiments are only explained roughly to an extent enabling the presentinvention to be understood and worked. Further, the numerical values andcompositions (materials) of the components are indicated as onlyillustrations. Therefore, the present invention is not limited to theembodiments explained below and can be modified in various ways to anextent not deviating from the scope of the technical ideas expressed inthe claims.

A first embodiment of the electrostatic chuck device according to thepresent invention will be explained with reference to FIG. 1 to FIG. 6.In this embodiment, the explanation will be given for the example of anelectrostatic chuck device applied to a sputtering system as thesubstrate film forming system.

FIG. 1 shows the configuration of a sputtering system in which theelectrostatic chuck device according to the first embodiment may beused. The basic parts of the configuration of this sputtering system arethe same as in the conventional system explained with reference to FIG.23. In FIG. 1, components the same as those explained in FIG. 23 areassigned the same reference numerals. Therefore, the configuration ofthe sputtering system will be only briefly explained. This sputteringsystem is comprised of a vessel 11 with an inside reduced in pressure byan external evacuation mechanism (not shown), a target attached to theceiling of the vessel 11 through a ring-shaped insulating member 12, amagnet 15 placed at a back side of the target 13 and fixed to a yokeplate 14, a substrate support 16 placed at a position facing the target13 and fixed to the bottom of the vessel 11, and an electrostatic chuckdevice 40, and a substrate temperature regulator 19 provided at thesubstrate support 16. The target 13 is supplied with voltage from asputter power source 31. A cylindrical shield member 20 is arrangedalong the inside surface of the circumferential wall of the vessel 11.

In FIG. 1, illustrations of the substrate conveyance robot,loading/unloading gates, lift pins for carrying and detaching thesubstrate 17 at the substrate support 16, mechanisms relating to theelectric discharge, mechanisms for introducing an Ar gas used for theelectric discharge and the like are omitted.

The electrostatic chuck device 40 according to the present embodimentprovided on the substrate support 16 is comprised of a dielectric plate41 with an embossed surface, a metal electrode 42 provided inside thedielectric plate 41, and an external DC power circuit 24 for supplying apredetermined voltage to the metal electrode 42.

The embossed part 43 of the surface of the dielectric plate 41 iscomprised of a plurality of projections 43 a, depressions 43 b, and anouter peripheral projection 43 c. The projections 43 a form extremelysmall columnar shapes. The surface of the embossed part 43 of thedielectric plate 41 is provided with conductor wiring 44 (shown in FIG.3 to FIG. 6) covering the top surfaces (substrate supporting surfaces)of all of the plurality of projections 43 a and electrically connectingall of the plurality of projections. The embossed part 43 and theconductor wiring 44 will be explained in detail later.

A hole 45 is formed at the center of the dielectric plate 41. This hole45 is provided in it with a conductor shaft 46. The bottom of theconductor shaft 46 has a conductor 47 connected to it. The conductor 47is led to the outside and is connected to the ground through a switch48.

The metal electrode 42 has a bipolar electrode structure comprised of aninside electrode 42 a and an outside electrode 42 b. The metal electrode42 is connected to an external DC power circuit 24 and is supplied witha predetermined voltage. The external DC power circuit 24 is providedwith a battery 24 a for supplying a plus voltage, a battery 24 b forsupplying a minus voltage, a ground terminal 24 c, and switches 24 d and24 e. The inside electrode 42 a is supplied with a plus voltage by thebattery 24 a, the switch 24 d, and a conductor 49. Further, the externalelectrode 42 b is supplied with a minus voltage by the battery 24 b, theswitch 24 e, and a conductor 50.

The substrate temperature regulator 19 is comprised of a thermocouple25, a power source/control mechanism 26, and a heating/cooling unit 27.

Further, a gas is introduced into the clearances 51 formed between thedielectric plate 41 and the substrate 17 from a gas supply source 28through a gas introduction path 29. The introduced gas maintains thepressure in the clearances 51 at a predetermined level. Further, theheat conduction of the gas holds the substrate 17 at a predeterminedtemperature.

FIG. 2 is a plan view of the dielectric plate 41 and shows the patternof formation of the embossed projections 43 a and the pattern ofarrangement of the metal electrode 42. In FIG. 2, for easierunderstanding, the state without the conductor wiring 44 is shown. FIG.3 is a view similar to FIG. 2, but showing the pattern of formation ofthe conductor wiring 44. FIG. 4 is a sectional view along the line A-Ain FIG. 2.

In FIG. 2 and FIG. 3, the region of the metal electrode 42 is shown byhatching. The metal electrode 42 is a bipolar electrode comprised of aninside disk-shaped electrode 42 a and an outside donut-shaped electrode42 b. The areas of the electrode surfaces of the inside electrode 42 aand the outside electrode 42 b are substantially the same. Further, theelectrode sections near the bottoms of the plurality of projections 43 aof the embossed part 43 are cut away at equal distances along the shapesof the embossed projections to form circular holes 51.

In this embodiment, as shown in FIG. 4, the inside electrode 42 a andthe outside electrode 42 b are supplied with a plus voltage from thebattery 24 a and a minus voltage from the battery 24 b respectively.When the inside and outside electrodes 42 a and 42 b are supplied withthe voltages, the embossed surface of the dielectric plate 41 is givencharges of signs corresponding to the electrode voltages. Since a closedcircuit is formed through the back of the substrate 17 being in contactwith the embossed projections 43 a and the like, the back surface of thesubstrate 17 as well is given charges of different signs from thesurface of the dielectric plate 41. The coulomb force acting between thecharges induced at the surface (embossed depressions) of the dielectricplate 41 and the charges at the back surface of the substrate 17 fixesthe substrate 17 on the dielectric plate 41.

The coulomb force acting between the surface of the dielectric plate 41and the substrate 17 is, as explained above, F=∈(V²/L²)A/8 in the caseof a bipolar electrode (when the plus and minus electrode areas are thesame).

AlN (aluminum nitride) with the good heat conductivity is used as thematerial of the dielectric plate 41. The substrate 17 arranged on thedielectric plate 41 is supported by a circular projection 43 c formedalong the outer periphery and the plurality of embossed projections 43a. The projections 43 a are columnar shaped. The height of theprojections 43 a and the projection 43 c is in the range of 5 μm to 15μm. The radius of the projections 43 a and the width of the outerperipheral projection 43 c are preferably determined so that the totalarea supporting the substrate 17 and contacting the back of thesubstrate becomes about 1.5% of the total area of the dielectric plate41.

In this embodiment, for example, when processing the substrate 17 havinga diameter of 300 mm, the diameter of the dielectric plate 41 is 300 mm,the projections 43 a of the embossed part 43 have diameters of 1 mm anda number thereof is about 150, and the width of the outer peripheralprojection 43 c is 1 mm. The plurality of projections 43 a is arrangedsymmetrically about the center of the dielectric plate 41. In FIG. 2,the diameters of the embossed projections 43 a are drawn larger thanthose in actuality to facilitate understanding.

The surface of the dielectric plate 41 is provided with theabove-mentioned conductor wiring 44 so that the plurality of projections43 a, which are the sections supporting the substrate 17 and being incontact with the same, and the outer peripheral projection 43 c areelectrically connected. The arrangement pattern of the conductor wiring44 is as shown in FIG. 3. The conductor wiring 44 forms interconnectingparts in the diametrical directions and interconnecting parts in thecircumferential directions. The interconnecting parts in the diametricaldirections are formed by a plurality of concentric circular parts. Theconductor wiring 44 is made of titanium, tungsten, molybdenum, tantalum,or nitrides etc. and is preferably abrasion resistant material. Further,the conductor wiring 44 is preferably made of materials havingcoefficients of heat expansion of the same extent as the dielectricplate 41.

The conductor wiring 44 is formed by sputtering, ion plating, or otherfilm forming methods. The thickness of the conductor wiring 44 isseveral μm or so. The conductor wiring 44 have good bondability with thedielectric plate 41 and will not peel off even if the temperature rises.The conductor wiring 44 is formed substantially symmetrically about thecenter of the dielectric plate 41 and so as to concentrate at the edgesof the hole 45 formed at the center of the dielectric plate 41. Byarranging the conductor wiring 44 point symmetrically, the distancesfrom the position of the ground part 52 at the center of the dielectricplate 41 to the plurality of projections 43 a are made equal and theelectrical resistance of the conductor wiring 44 are made the same. Theedges of the hole 45 are inclined. At the inclined part of the hole 45,the conductor wiring 44 is connected to the conductor shaft 46 fillingthe hole 45. The conductor shaft 46 is connected to the switch 48 of anexternal circuit. The conductor shaft 46 is connected to the groundthrough the switch 48. The conductor wiring 44 is controlled to thegrounded state or the floating state by the switch 48. The conductorwiring 44, and the external circuit from the conductor shaft 46 to theswitch 48, or the conductors 47, are only naturally electricallyinsulated from the substrate temperature regulator 19 and the vessel 11.

The processing of the substrate by the sputtering system according tothe present embodiment is basically the same as explained with respectto the conventional system. In this embodiment, preferably the insideelectrode 42 a of the metal electrode 42 is supplied with a voltage inthe range of +200 V to +1000 V, while the outside electrode 42 b issupplied with a voltage in the range of −200 V to −1000 V.

Next, the clamping action of the substrate by the electrostatic chuckdevice 40 will be explained with reference to FIG. 5 and FIG. 6.

The substrate (a silicon substrate, for example) 17 is placed on thedielectric plate 41. When the inside and outside electrodes 42 a and 42b are supplied with predetermined voltages of opposite polarity, thesurface of the dielectric plate 41 gets charged corresponding to thepotentials of the corresponding electrode parts, while the facingsurface of the back of the substrate 17 gets charged with opposite signscorresponding to the corresponding locations of the surface of thedielectric plate. As a result, the electrostatic force (coulomb force)between the regions of the embossed depressions 43 b of the surface ofthe dielectric plate 41 and the back of the substrate corresponding tothese regions alone clamps and fixes the substrate 17 to the dielectricplate 41. That is, the inside electrode 42 a is supplied with a plusvoltage by the battery 24 a, while the outside electrode 42 b issupplied with a minus voltage by the battery 24 b. The surface of theembossed part of the dielectric plate 41 corresponding to the insideelectrode 42 a gets charged to be plus, while the surface of theembossed part of the dielectric plate 41 corresponding to the outsideelectrode 42 b gets charged to be minus. The substrate 17 is relativelylow in resistance, so when the inside and outside electrodes 42 a and 42b are supplied with predetermined voltages, current easily flows nearthe surface of the back of the substrate 17, a minus charge occurs atthe section of the back of the substrate facing the plus electrode, aplus charge occurs at the section of the back of the substrate facingthe minus electrode, and the potential of the substrate becomessubstantially the same in absolute value as the potential of the metalelectrode 42. When the charges migrate at the back of the substrate 17,the power circuit 24 and the substrate 17 form a closed circuit and aflow of charges occurs at this closed circuit.

The electrode parts near the bottom of the embossed projections 43 a areremoved as explained above to form the circular holes 51. As a result,the charges occurring near the top surfaces of the embossed projections43 a are reduced compared with the conventional electrostatic chuckdevice. This is because the amount of charges is inversely proportionalto the distance between the metal electrode 42 and the surface of thedielectric plate 41. That is, the relationship of σ=∈₀V/d stands. Here,σ is the charge per unit surface area, V is the electrode voltage, and dis the distance between the electrode and surface.

Further, as explained above, since the embossed projections 43 a aremade small in shape and the areas of the top surfaces of the embossedprojections 43 a are also made extremely small, the amounts of chargesoccurring at the top surfaces of the embossed projections 43 a arereduced by this as well.

The force dF per unit area acting between the substrate 17 and thedielectric plate 41 is dF=σ²/∈₀. Therefore, the clamping force on thesubstrate 17 at the projections 43 a of the embossed part 43 can be madesmaller compared with the conventional electrostatic chuck device.

Further, the plurality of embossed projections 43 a and the outerperipheral projection 43 c are in contact with the back of the substrate17. In this case, since the conductor wiring 44 covering the embossedprojections 43 a and the outer peripheral projection 43 c is actually incontact with the back of the substrate 17, it becomes substantially thesame potential as the contacted parts of the substrate. That is,although, before the contact, the conductor wiring 44 are given chargesof different signs by electrostatic induction in accordance with thecorresponding surface charges of the dielectric plate 41, the conductorwiring 44 tries to become the same potential as the substrate 17 by thecontact with the substrate 17. After the contact, the conductor wiring44 becomes substantially the same potential as the substrate 17, whilethe conductor wiring 44 is given charges of the same signs as thecharges induced at the back of the substrate 17. That is, the contactresistance between the dielectric plate 41 and the conductor wiring 44is larger than the contact resistance between the conductor wiring 44and the substrate 17, so the conductor wiring 44 becomes substantiallythe same potential as the substrate 17 and is given charges of the samesigns as the charges at the back of the substrate 17. Therefore, at thecontact parts between the surfaces of the embossed projections 43 a andouter peripheral projection 43 c, or the conductor wiring 44, and thesubstrate 17, no electrostatic force (coulomb force) is generated and noclamping force acts. The clamping force for fixing the substrate 17 onlyoccurs between the embossed depressions 43 b and the substrate 17.Therefore, the Johnsen-Rahbek effect also does not occur at thesubstrate and surfaces of the embossed projections (substrate supportingsurfaces) as had occurred in the conventional electrostatic chuckdevices. No strong force acts between the substrate 17 and the embossedprojections 43 a of the dielectric plate 41, so there is very littlegeneration of particles due to rubbing between the two.

Here, the conductor wiring 44 on the embossed projections 43 a becomesthe same potential as the corresponding sections of the substrate 17(minus potential at right side section in FIG. 6 and plus potential atleft side section of FIG. 6). Due to the presence of the charges ofdifferent signs induced at the dielectric plate side at the interfacewith the dielectric plate 41 at the lower side of the conductor wiring44 (plus charge at right side section in FIG. 6 and minus charge at leftside section of FIG. 6), the charges migrate and dissipate and the forceis generated by the JR effect at the interface. The phenomenon occurringat the interface, however, has nothing to do with clamping of thesubstrate. Further, in FIG. 5 and FIG. 6, the section of the conductorwiring 44 corresponding to the inside electrode 42 a and the section ofthe conductor wiring 44 corresponding to the outside electrode 42 b areconnected through the resistance element 52 as an electrical circuit.The section of the conductor wiring 44 corresponding to the insideelectrode 42 a and the section of the conductor wiring 44 correspondingto the outside electrode 42 b differ in signs of the charges induced asexplained above. The charges of these different signs partially migrateand dissipate through the resistance element 52.

The force clamping the substrate 17 in the present embodiment will becalculated next. The force at work, as explained above, is F=∈(V²/L₀²)A/8 (when the electrode areas are the same between the plus electrodeand minus electrode). Here, ∈ is the dielectric constant, V is thevoltage, L₀ is the distance between the surface of the metal electrodeand the back of the substrate, and A₀ is substantially the area of themetal electrode 42. The clamping force required is strictly determinedby the area which does not include the area of the conductor wiring 44.The clamping force is proportional to the square of the supplied voltageand the electrode area and is inversely proportional to the square ofthe distance between the substrate and dielectric plate surface. Here,when processing a substrate with a diameter of 300 mm, it is assumedthat the diameter of the dielectric plate serving as the substratesupport is also 300 mm, the electrode is a disk with a diameter of 298mm, and the total area of the outer peripheral projection with a widthof 1 mm and embossed projections with a diameter of 1 mm being incontacting with the substrate is 1.5% of the whole area.

The force acting when the supplied voltage is 200 V to 500 V is 500 N to3200 N, and 50 Torr to 370 Torr in terms of pressure. This issufficiently above the counterforce due to the approximately 10 Torrpressure difference between the pressure caused by the introduction ofthe gas to the clearances 51 and the internal pressure of the vessel 11and enables stable clamping and fixing.

When the surface of the substrate is covered by SiO₂, however, migrationof the charges at the substrate contact parts is determined by themigration of the charges at the SiO₂ layer and is not as easy as withthe case of a silicon substrate alone. Further, the substrate and thedielectric plate do not easily become the same potential at the embossedpart, so this calculation is not necessary accurate. However, nomigration of charges occurs such as with the case of contact betweendielectrics, so the clamping force at the embossed part is reducedcompared with the prior art.

After the substrate 17 finishes being processed, the voltage stops beingsupplied to the electrode layer 42, and the metal electrode 42 andconductor shaft 46 are connected to the ground part by switches of anexternal circuit. The conductor wiring 44 connected to the conductorshaft 46 is also grounded. In this case, when the metal electrode 42becomes the ground potential, the separation of the charges due toelectrostatic induction is eliminated at the inside of the facingsubstrate 17 and the charges induced at the back are dissipated. Due tothe conductor wiring 44 being grounded, the charges at the surfaces ofthe embossed projections 43 a and the grounded back of the substrateflow out through the ground circuit. Due to this, the clamping force dueto the embossed part 43 of the dielectric plate 41 rapidly falls.

Further, the charges induced at the back of the dielectric plate 41remain and become a cause of residual clamping force even after thesupply of voltages to the metal electrode 42 is stopped. But theresidual charges at the surface of the dielectric plate 41 migrate notonly to the metal electrode 42, but also the conductor wiring 44 andflow out to the ground circuit. Therefore, the residual charges at thesurface of the dielectric plate rapidly drop more than in the priorarts. Therefore, the residual clamping force between the surface of thedielectric plate and the substrate also rapidly declines compared withthe prior art.

The release of the charges can be superior compared with the prior arteven when the substrate is covered with SiO₂. The reason is that theonly grounded electrode where the charges were released in the prior artwas the internal metal electrode, but in the present embodiment theconductor wiring 44 are added in addition to the metal electrode 42. Inparticular, the charges near the conductor wiring 44 rapidly decline.This is because the speed of the fall in a residual charge is heavilydependent on the distance to the electrode where the charge dissipates.As a result, the overall residual charge also falls and the residualclamping force between the surface of the dielectric plate and thesubstrate rapidly falls compared with the prior art.

Due to the above, the substrate clamping force drops off instantaneouslyfrom when voltages stop being supplied to the inside and outsideelectrode layers 42 a and 42 b and the clamping force due to theresidual charge does not continue long. Therefore, even if the substratestarts to be unloaded immediately after the voltages stop being suppliedto the metal electrode 42, the substrate will not vibrate and nopositional deviation will occur.

According to the above electrostatic chuck device, when inspectedexperimentally, the about 50,000 particles generated at the back whenprocessing the substrate of a diameter of 300 mm in the prior art wasreduced to less than about 5000. Due to this, the yield in productionalso became extremely improved.

The electrostatic chuck device according to the above embodiment can beapplied to CVD for depositing thin films on the substrates or dryetching for processing the thin film in addition to sputtering. Further,in the present embodiment, the explanation was given with respect to abipolar electrode, but it may be similarly applied to a unipolarelectrode as well. In the case of a unipolar electrode as well, circularholes 51 are formed at locations corresponding to the embossedprojections and conductor wiring 44 having the above pattern ofarrangement are formed on the surface of the embossed sections 43. Inthe case of a unipolar electrode, it is sufficient for example to makethe inside electrode 42 a and outside electrode 42 b integrally andsupply a plus or minus voltage.

According to the above-mentioned first embodiment, it is possible toprovide an electrostatic chuck device for clamping and fixing asubstrate by the coulomb force between the embossed surface of adielectric plate and the back of the substrate which covers the topsurfaces of the plurality of embossed projections by conductor wiringand electrically connects all embossed projections, so has no strongforce acting on the contact parts between the substrate and dielectricplate and suppresses the generation of particles due to rubbing. Aconducting path is provided for the escape of the charges by groundingthe conductor wiring, so there are little residual charges, the clampingforce can be made to drop off instantaneously after the voltages stopbeing supplied to the electrode, and therefore the substrate can betaken out and conveyed stably after processing the substrate. Due tothis, the yield is high and substrates can be processed with a highoperating rate.

Next, an electrostatic chuck device according to a second embodimentwill be explained with reference to FIG. 7 to FIG. 12. In thisembodiment as well, the explanation will be given of an example of anelectrostatic chuck device applied to a sputtering system.

In FIG. 7, the basic sections of the sputtering system are the same asin the conventional system of FIG. 23. Components the same as thecomponents explained in FIG. 23 are assigned the same referencenumerals, and detail explanations thereof are omitted.

The electrostatic chuck device 40 according to the present embodimentprovided on the substrate support 16 is comprised of a dielectric plate122 with an embossed surface, a metal or other electrode layer 141provided on the surface of the dielectric plate 122, and an external DCpower circuit 24 for supplying the electrode layer 141 with apredetermined voltage.

The embossed part 121 on the surface of the dielectric plate 122 iscomprised of a plurality of projections 121 b, depressions 121 c, and anouter peripheral projection 121 d. The projections 121 b form columnarshapes. The outer peripheral projection 121 d has a ring shape. Theouter peripheral projection 121 d is included in the “projections” inconcept. The embossed part 121 of the dielectric plate 122 formsclearances 121 a at the back of the substrate 17. At the embossed part121 of the dielectric plate 122, all of top surfaces (substratesupporting surfaces) of the plurality of projections 121 b are providedwith conductor layers 142. As the material of the dielectric plate 122,AlN (aluminum nitride) having good heat conductivity is used.

The electrode layer 141 is arranged at the bottom of the depressions 121c of the embossed part 121. The electrode layer 141 has the structure ofa bipolar electrode comprised of a disk-shaped inside electrode layer141 a and ring-shaped outside electrode layer 141 b. The electrode layer141 is produced from tungsten, molybdenum, tantalum, or another metal ora carbon-based conductor having a coefficient of heat expansion of thesame extent as the dielectric layer 122.

FIG. 9 shows a plan view of the dielectric plate 122 and shows thepattern of formation of the embossed projections 121 b and the patternof arrangement of the electrode layer 141. In FIG. 9, the diameters ofthe embossed projections 121 b are drawn larger than in actuality so asto facilitate understanding. In FIG. 9, the region of the electrodelayer 141 is shown by hatching. The electrode layer 141 is comprised oftwo parts of an inside disk-shaped electrode 141 a and an outsidedonut-shaped electrode 141 b. The electrode layer 141 is provided at thelocation of the embossed depressions 121 c of the surface of thedielectric plate 122. Note that the embossed projections 121 b have theconductor layer 142 formed on them, so FIG. 9 shows circular conductorlayers 142 at the locations of the embossed projections 121 b. Further,the rim section of the outside of the dielectric plate 122 is formedwith a ring-shaped outer peripheral projection 121 d and formed on topof that with a ring-shaped conductor layer 143.

The electrode layer 141 is formed by ion plating etc. and has athickness of several μm to several tens of μm or so. The electrode layer141 has good bondability with the dielectric plate 122 and does not peeloff when the temperature rises. The electrode layers 141 a and 141 bhave a DC current source connected to them through an external circuit.That is, the electrode layer 141 is connected to the external DC powersource 24 and supplied with a predetermined voltage. The external DCpower source 24 is provided with a battery 24 a for supplying a plusvoltage, a battery 24 b for supplying a minus voltage, a ground terminal24, and switches 24 d and 24 e. The inside electrode layer 141 a issupplied with a plus voltage by the battery 24 a, switch 24 d, andconductor 143, while the outside electrode layer 141 b is supplied witha minus voltage by the battery 24 b, switch 24 e, and conductor 144.Further, the electrode layers 141 a and 141 b are grounded by the groundterminal 24 c of the external DC power circuit 24.

When the inside electrode layer 141 a and the outside electrode layer141 b are supplied with a plus voltage from the battery 24 a and a minusvoltage from the battery 24 b respectively, the surfaces of the embossedprojections 121 b of the dielectric plate 122 are given charges of signscorresponding to the electrode voltages.

The electrode layer 141 is formed by forming a film on the dielectricplate 122, so is electrically insulated from the substrate temperatureregulator 19. Further, the conductors 143 and 144 forming the electricalconnections with the external DC power circuit 24 are also electricallyinsulated from the substrate temperature regulator 19 or vessel 11.

As shown enlarged in FIG. 8, the top surfaces of the embossedprojections 121 b are formed with conductor layers 142. The conductorlayers 142 are made of a metal having a coefficient of heat expansion ofthe same extent as the dielectric plate 122 and, for example, may betungsten, molybdenum, tantalum, or, other than a metal, a carbon-basedmaterial. The conductor layers 142 are electrically insulated from theelectrode layer 141. The conductor layers 142 are similarly formed byion plating etc. and have a thickness of several Fm to several tens ofFm. They have a good bondability with the dielectric plate 122 and donot peel off even if the temperature rises. The top surfaces of theembossed projections 121 are inherently sections directly being incontact with the substrate 17. A conductor layer 142 is also formed atthe surface of the ring-shaped outer peripheral projection 121 d of thedielectric plate 122 contacting the substrate 17 in addition to theembossed projections 121 b.

To ensure insulation between the electrode layer 141 (141 a, 141 b) andthe conductor layers 142, as shown in FIG. 10 and FIG. 11, preferablythe range where the conductor layers 142 are formed is either madeinside from the range of the top surfaces of the embossed projections121 b or the range where the dielectric layer 142 is formed is madeinside from the range of the top surfaces of the embossed projections121 b and the electrode layer is not formed near the peripheries of thestep differences of the embossed part. That is, preferably it is notarranged linearly in the height direction at locations where stepdifferences are formed between the edge parts of the electrode layer andthe edge parts of the conductor layers.

Further, gas is introduced into the clearances 121 a formed between thedielectric plate 122 and the substrate 17 from the gas supply source 28through the gas introduction path 29. The introduced gas holds thepressure in the clearances 121 a at a predetermined pressure. Further,the heat conduction of the gas holds the substrate 17 at a predeterminedtemperature.

The processing of the substrate by the sputtering system according tothe present embodiment is basically the same as the content explainedwith respect to the above-mentioned embodiment. In this embodiment,preferably the inside electrode 141 a of the electrode layer 141 issupplied with a voltage in the range of +200 to +1000 V, while theoutside electrode 141 b is supplied with a voltage in the range of −200V to −1000 V. When the electrodes 141 a, 141 b are supplied withvoltages, as shown in FIG. 12, the back of the facing substrate 17 isgiven charges of different signs from the signs of the electrodepotential, and the electrostatic force clamps the substrate 17 and fixesit on the dielectric plate 122.

Next, the action of the electrostatic chuck device 40 in clamping asubstrate will be explained in detail with reference to FIG. 12.

The substrate 17 is placed on the dielectric plate 22. When the insideand outside electrodes 141 a and 141 b are supplied with predeterminedvoltages, the back surface of the substrate 17 is given charges of signscorresponding to the potential of the corresponding electrodes. As aresult, the electrostatic force fixes the substrate 17 to the dielectricplate 122. The substrate 17 is relatively low in resistance, so when theinside and outside electrodes 141 a and 141 b are supplied withpredetermined voltages, current easily flows near the surface of theback of the substrate 17, a minus charge occurs at the section of theback of the substrate facing the plus electrode layer, a plus chargeoccurs at the section of the back of the substrate facing the minuselectrode layer, and the potential of the substrate becomessubstantially the same in absolute value as the potential of theelectrode layer 141. When the charge migrates at the back of thesubstrate 17, the power circuit 24 and the substrate 17 form a closedcircuit and a flow of charges occurs at this closed circuit.

On the other hand, the top surfaces of the embossed projections 121 bare in contact with the back of the substrate 17, but the dielectriclayers 142 of the projections 121 b become the same potential as theback sections of the substrate 17 contacted. Therefore, no electrostaticforce is generated between the surfaces of the embossed projections 121b and the substrate 17 and no electrostatic force acts. Therefore, theJohnsen-Rahbek effect does not occur at the contact parts of thesubstrate 17 and the embossed parts 121 of the dielectric plate 122,that is, the embossed surface, and no strong force acts there, so thereis very little generation of particles due to rubbing.

Here, the dielectric layers 142 at the top surfaces of the embossedprojections 121 b become substantially the same in potential as thesubstrate 17 (minus potential in FIG. 12), but the presence of chargesof different signs (plus charge in FIG. 12) induced at the dielectricplate side of the interface with the dielectric plate 122 below it(interface with top surfaces of embossed projections) causes themigration and dissipation of the charges and generation of force by theJohnsen-Rahbek effect at the interface. However, this phenomenonoccurring at the interface has nothing to do with the clamping of thesubstrate.

The force clamping the substrate 17 in the present embodiment will becalculated next. The force at work, as explained above, is F=∈(V²/L₀²)A/8 (when the electrode areas are the same between the plus electrodeand minus electrode). Here, ∈ is the dielectric constant, V is thevoltage, L₀ is the distance between the surface of the metal electrodeand back of the substrate, and A₀ is substantially the area of the metalelectrode 141. The clamping force is proportional to the square of thesupplied voltage and the electrode area and is inversely proportional tothe square of the distance between the substrate and dielectric platesurface.

Here, assume the case of processing a substrate of a diameter of 300 mm,making the diameter of the dielectric plate 122 serving as the substratesupport also 300 mm, making the surface of the electrode layer 141 adisk of a diameter of 298 mm, and assuming the total area of the outerperipheral projection of a width of 1 mm and embossed projections ofdiameters of 1 mm contacting the substrate 1% of the total area.

The force acting when the supplied voltage is 200 V to 500 V is 500 N to3200 N, or 50 Torr to 370 Torr in terms of pressure. This issufficiently above the counterforce due to the pressure differencebetween the pressure caused by the introduction of the gas to theclearances 121 a and the internal pressure of the vessel 11 and enablesstable clamping and fixing.

When the surface of the substrate is covered by SiO₂, however, migrationof the charges at the substrate contact parts is determined by themigration of the charges at the SiO₂ layer and is not as easy as withthe case of a silicon substrate alone. Further, the substrate and thedielectric plate do not easily become the same potential at the embossedpart, so this calculation is not necessary accurate. However, nomigration of charges occurs such as with the case of contact betweendielectrics, so the clamping force at the embossed part is reducedcompared with the prior art.

After the substrate 17 finishes being processed, the voltage stops beingsupplied to the electrode layer 141 and the electrode layer 141 isconnected to the ground part 24 c by the switches 24 d and 24 e of anexternal circuit. When the electrode 41 becomes the ground potential,the separation of the charges due to electrostatic induction iseliminated at the inside of the facing substrate 17 and the chargesinduced at the back of the substrate are dissipated. As a result, theelectrostatic force which had acted between the electrode layer 141 andthe substrate 17 is rapidly decreased and the clamping force dissipates.

However, since the charges induced at the sections of the dielectricplate at the surfaces of the projections 121 b of the embossed part 121remain, charges of different signs remain at the back sections of thesubstrate near the projections 121 b. However, the dielectric layers 142formed at the surfaces of the embossed projections 121 b continue to beabout the same potential as the substrate 17, no electrostatic forceacts between the substrate and the dielectric plate, and no clampingforce is generated. No clamping force is generated between the substrateand the dielectric plate due to the residual charges of those sections.

Due to the above, the substrate clamping force drops off instantaneouslyfrom when voltages stop being supplied to the inside and outsideelectrode layers 141 a and 141 b and the clamping force due to theresidual charges does not continue long. Therefore, even if thesubstrate starts to be unloaded immediately after the voltage stopsbeing supplied to the metal electrode 142, the substrate will notvibrate and not deviate in position.

According to the electrostatic chuck device according to the presentinvention, when inspected experimentally, the about 50,000 particlesgenerated at the back when processing a substrate of a diameter of 300mm in the prior art was reduced to less than about 5000. Due to this,the yield in production also became extremely improved.

The electrostatic chuck device according to the above embodiment can beapplied to CVD for forming a thin film on a substrate or dry etching forprocessing a thin film in addition to sputtering. Further, in thepresent embodiment, the explanation was given with respect to a bipolarelectrode, but the invention may be similarly applied to a unipolarelectrode as well.

According to the above second embodiment, it is possible to provide anelectrostatic chuck device for clamping and fixing a substrate by thecoulomb force between the embossed surface of a dielectric plate and theback of a substrate which forms an electrode layer on the surface of theembossed depressions and forms dielectric layers on the top surfaces ofthe plurality of embossed projections, so holds the contact parts withthe substrate at the same potential, has no strong force acting on thecontact parts between the substrate and dielectric plate, and suppressesthe generation of particles due to rubbing. After the substrate finishesbeing processed, the clamping force can be made to drop offinstantaneously after the voltage stops being supplied and therefore thesubstrate can be taken out and conveyed stably. Due to this, the yieldis high and substrates can be processed with a high operating rate.

Next, an electrostatic chuck device according to a third embodiment willbe explained with reference to FIG. 13 and FIG. 14. In this thirdembodiment, the explanation will be given showing only the section ofthe electrostatic chuck device 40.

-   In FIG. 13 and FIG. 14, to facilitate the explanation, the    configuration of a bipolar electrostatic chuck device illustrated    enlarged in the thickness direction is shown. FIG. 13 is an enlarged    longitudinal sectional view of an electrostatic chuck device 40,    while FIG. 14 is a longitudinal sectional view of the location “A”    in FIG. 13. The electrostatic chuck device 40 is comprised of metal    electrodes 201 and 202, thin dielectric layers 203, and a thick    insulating case 204. The metal electrodes 201 and 202 are formed on    their top surfaces with a plurality of embossed projections 205.    Normally, the embossed projections 205 are circular in shape in a    horizontal cross section. However, the embossed projections 205 are    not limited to this shape. When the horizontal sectional shape of    the embossed projections 5 is circular, the diameter is in the range    of 1 to 5 mm. The size of the diameter is not important, but a    smaller diameter is more preferable to control the generation of    particles. The height (h) of the embossed projections 205 is about    10 μm or larger. The height can also be increased to several mm. The    top surfaces of the embossed projections 205 are covered by the thin    dielectric layers 203. The thickness of the dielectric layers 203 is    preferably made smaller than 1 μm. The reduction of the thickness    increases the efficiency of declamping of the substrate. The    electrical resistance of the dielectric layers 203 is not important.    However, a dielectric material doped with a required impurity is    more advantageous.

The thickness of the metal electrodes 201 and 202 are not important andmay be in the range of several mm to several cm. Each of the metalelectrodes 201 and 202 may or may not be provided with a cooling orheating mechanism. For example, both of the metal electrodes 201 and 202shown in FIG. 13 have cooling mechanisms (208, 209, 210, 211). Thecooling mechanisms are comprised of cooling medium inlets (208, 210),cooling medium exits (209, 211), and passages 212 for carrying thecooling medium.

The surfaces of the metal electrodes 201 and 202 are covered by aninsulating material 204 everywhere except for the top sides. The objectis to electrically insulate the metal electrodes 201 and 202 from theremaining parts of the hardware. Further, the surfaces of the sides andbottom of the insulating material 204 are covered by a metal case 215.The metal electrodes 201 and 202 are electrically connected with twodifferent DC voltage sources 206 and 207.

Next, the operation of the bipolar electrostatic chuck device will beexplained. When giving two different bias voltages to the metalelectrodes 201 and 202, as shown in FIG. 15, charges are generated onthe surfaces of the metal electrodes 201 and 202 and the substrate 213.Two electrostatic forces (F₁, F₂) are generated based on thedistribution of the charges. The force F₁ is generated between thesubstrate 213 and the surface of the metal electrode called the“depressions 216”. The force F₂ is generated between the substrate 213and the top surfaces of the metal embossed projections 205. The height(h) of the embossed projections 205 is larger than 10 μm and thethickness (t) of the dielectric layers 203 is smaller than 1 μm.Therefore, the force F₁ is smaller by about four orders than the forceF₂. Therefore, the substrate 213 is inherently fixed on theelectrostatic chuck device 40 by the force F₂.

Ease of declamping of the substrate is achieved by the aboveconfiguration. An accumulation of the charges occurs on the top surfaceof the dielectric layers 203 when a bias voltage is given to the metalelectrodes. This state is shown in FIG. 16. However, the thickness ofthe dielectric layers 203 is about three orders smaller than that of theconventional device. Therefore, when the metal electrodes 201 and 202are grounded to release the substrate, the accumulated charges arefinally neutralized by the current re-flow process. Further, use ofdielectric layers doped with an impurity further accelerates thedeclamping process.

The reduction in the particles generated is achieved by the aboveconfiguration. In the electrostatic chuck device 40 according to thepresent embodiment, the dielectric layers 203 on the metal embossedprojections 205 are extremely thin. For example, the thickness is about100 nm. Therefore, the increase in the electrostatic force along withthe elapse of time due to the migration of charges through the thindielectric layers 203 does not result in any important changes. Further,since the dielectric layers 203 are extremely thin, the migration of thecharges to the top surfaces of the thin dielectric layers 203 iscompleted within an extremely short time period. Therefore, it becamepossible to accurately calculate the voltage which has to be supplied togenerate the electrostatic force required. Further, this force can beconsidered to be almost constant and does not remarkably increase alongwith the elapse of time. This prevents the generation of too strong anelectrostatic force and reduces the generation of particles.

The electrostatic chuck device of the third embodiment is furthercharacterized by a reduction in particle contamination. The embossedprojections 205 produced on the metal electrodes 201, 202 areconsiderably higher than those of the conventional devices. If particlesare generated, a larger percentage of the particles 217 deposit in thedepressions 216 of the metal electrodes 210, 202. This condition isshown in FIG. 17. The reduction in particles sticking on the back of thesubstrate 213 may be explained as being due to two reasons. The firstreason is that the embossed projections 205 are larger in height, forexample, are about 1 mm, so re-sticking of particles due to turbulencein the inert gas is reduced. The second reason is the larger distancebetween the back of the substrate and the particles is equal to theheights of the embossed projections. Due to this, the electrostaticforce between the particles and the back of the substrate is reduced.This minimizes the sticking of particles on the back of the substratedue to electrostatic force. These two processes help to minimize thenumber of particles at the back of the substrate.

Next, an electrostatic chuck device according to a fourth embodimentwill be explained with reference to FIG. 18 and FIG. 19. In theelectrostatic chuck device 40 of the fourth embodiment, a single metalelectrode 218 is used. The configuration of the electrostatic chuckdevice is called a unipolar electrostatic chuck device. A longitudinalsectional view of this electrostatic chuck device is shown in FIG. 18,while an enlarged view of the section B in FIG. 18 is shown in FIG. 19.Except for using the single metal electrode 218, the rest of theconfiguration in the fourth embodiment is the same as that explained inthe third embodiment. Components the same as the components explained inthe third embodiment are assigned the same reference numerals.

The top surface of the metal electrode 218 has a plurality of embossedprojections 205. The height of these embossed projections 205 is largerthan 100 μm. The top parts of the embossed projections 205 are coveredby extremely thin dielectric layers 203. The thickness of the dielectriclayers 203 are smaller than 1 μm. The thickness of the metal electrode218 is not important and may be in the range of several mm to severalcm. The metal electrode 218 may or may not include a cooling or heatingmechanism. In FIG. 18, for example, a cooling mechanism (208, 209, 212)is shown. The metal electrode 218 is insulated by being placed on aninsulating block 204 and is connected to a battery 206.

The principle of operation of the fourth embodiment is the same as thatexplained in the third embodiment. However, to operate the electrostaticchuck device, there must be plasma above the substrate 213. This plasmacreates the electrical connection required for passing a DC currentthrough the substrate 213. Therefore, this embodiment can only operatein the presence of plasma. All of the advantages obtained in the thirdembodiment etc., in particular the ease of release of the substrate andthe reduced particles can also be obtained in the fourth embodiment.

Next, an electrostatic chuck device according to a fifth embodiment willbe explained with reference to FIG. 20. The fifth embodiment iscomprised as a bipolar electrostatic chuck device 40 having two metalelectrodes (221, 222) or a unipolar electrostatic chuck device havingjust one metal electrode. To facilitate the explanation, this embodimentwill be explained by using the configuration of a bipolar electrostaticchuck device. The metal electrodes 221 and 222 are made by thin metalsheets. The thickness of the metal electrodes 221 and 222 are notimportant and may be in the range of 0.5 mm to 10 mm. These metalelectrodes 221, 222 are insulated from each other electrically by theinsulating material 223 and are placed on another metal base 219. Themetal base 219 is provided with a cooling or heating mechanism formaintaining the metal base 219 at a predetermined temperature. The metalelectrodes 221, 222 are connected to the batteries 206, 207 in aseparated state by the switches 206A and 207A. Except for this, the restof the configuration is the same as that explained in the thirdembodiment.

The operating principle and advantages of the fifth embodiment are thesame as those explained in the third embodiment. Here, the only point ofdifference is that the metal electrodes 221 and 222 themselves do nothave cooling or heating mechanisms. Instead, the metal base 219 includesa cooling or heating mechanism. In this way, heat is conducted from themetal electrodes 221 and 222 to the metal base 219 through an insulatingmaterial 223.

Next, an electrostatic chuck device 50 according to a sixth embodimentwill be explained with reference to FIG. 21. This embodiment is anexpansion of the above embodiments. FIG. 21 is a longitudinal sectionalview of the sixth embodiment. To facilitate the explanation, theconfiguration explained in the fourth embodiment is used. Therefore, thehardware configuration of the sixth embodiment is substantially the sameas that explained in the fourth embodiment. The only difference is thatthe metal electrode 218 is connected to an rf power source 230 through amatching circuit 231 in addition to the battery 206. In this case, a rfcutoff filter 232 is added to the DC power connection.

The principle of operation of the electrostatic chuck device in thesixth embodiment is the same as that explained in the fourth embodiment.However, here, the metal electrode 218 acts as a rf electrode forgenerating plasma or an rf electrode for generating self bias voltage byrf bonding with the plasma over the entire surface of the substrate 213.The frequency of the rf current is not important, but is in the rangefrom 100 kHz to 100 MHz.

Next, the electrostatic chuck device 40 according to a seventhembodiment will be explained with reference to FIG. 22. FIG. 22 is apartial sectional view of the seventh embodiment. The configuration ofthe electrostatic chuck device according to the seventh embodiment isthe same as the above embodiments except for the section of the topsurface of the electrostatic chuck device.

The structure of the top surface of the metal electrode 241 in theseventh embodiment is shown in FIG. 22. The configuration of the metalelectrode 241 is substantially the same as explained in previousembodiments. However, a thin dielectric layer 242 is applied over theentirety of the metal electrode 241. Except for this change, the rest ofthe configuration is the same as that explained in the aboveembodiments. In particular, the thickness of the dielectric layer 242 onthe top surface of the embossed layer 205 is selected to be thatexplained in the third embodiment.

The advantages of the seventh embodiment are the same as those explainedin the above embodiments. In addition, this configuration withstands ahigher voltage applied to the metal electrodes (201, 202, or 218).

While the invention has been described with reference to specificembodiments chosen for purpose of illustration, it should be apparentthat numerous modifications could be made thereto by those skilled inthe art without departing from the basic concept and scope of theinvention.

The present disclosure relates to subject matter contained in JapanesePatent Application No. 2002-177380 and Japanese Patent Application No.2002-177381 filed on Jun. 18, 2002, and Japanese Patent Application No.2002-309915 filed on Oct. 24, 2002, the disclosures of which areexpressly incorporated herein by reference in their entirety.

1. An electrostatic chuck device comprising: a dielectric plate having asurface embossed to have a plurality of projections and depressions, anelectrode formed in the depressions, an external power circuit forswitching the electrode to be connected with a battery or a groundterminal, and a conductor wiring configured to cover a top surface ofall of the projections and electrically connects each of theprojections, wherein the electrode is divided to have a first electrodeand a second electrode which are mutually isolated, a surrounding areaof each of the projections in the dielectric plate is formed to have asecond depression hollowed along a shape of the projection.
 2. Anelectrostatic chuck device as set forth in claim 1, wherein theconductor wiring comprises a first conductor wiring in a diameterdirection and second conductor wirings in a circumference direction, andthe second conductor wirings are located as concentric circles.
 3. Anelectrostatic chuck device as set forth in claim 1, wherein the seconddepression is a round hole and the conductor wiring is not formed on asurface of the round hole.